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LibJS/Bytecode: Thread the bytecode interpreter

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This commit converts the main loop in Bytecode::Interpreter to use a
label table and computed goto for fast instruction dispatch.

This yields roughly 35% speedup on the for loop microbenchmark,
and makes everything else faster as well. :^)
This commit is contained in:
Andreas Kling 2024-05-06 16:44:45 +02:00
commit f4af056aa9
Notes: sideshowbarker 2024-07-17 17:06:59 +09:00
1 changed files with 268 additions and 211 deletions
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187
Userland/Libraries/LibJS/Bytecode/Interpreter.cpp
View file

@ -342,76 +342,111 @@ void Interpreter::run_bytecode(size_t entry_point)
TemporaryChange change(m_program_counter, Optional<size_t&>(program_counter));
// Declare a lookup table for computed goto with each of the `handle_*` labels
// to avoid the overhead of a switch statement.
// This is a GCC extension, but it's also supported by Clang.
static void* const bytecode_dispatch_table[] = {
#define SET_UP_LABEL(name) &&handle_##name,
ENUMERATE_BYTECODE_OPS(SET_UP_LABEL)
};
#define DISPATCH_NEXT(name) \
do { \
if constexpr (Op::name::IsVariableLength) \
program_counter += instruction.length(); \
else \
program_counter += sizeof(Op::name); \
auto& next_instruction = *reinterpret_cast<Instruction const*>(&bytecode[program_counter]); \
goto* bytecode_dispatch_table[static_cast<size_t>(next_instruction.type())]; \
} while (0)
for (;;) {
start:
bool will_return = false;
bool will_yield = false;
for (;;) {
auto& instruction = *reinterpret_cast<Instruction const*>(&bytecode[program_counter]);
goto* bytecode_dispatch_table[static_cast<size_t>((*reinterpret_cast<Instruction const*>(&bytecode[program_counter])).type())];
switch (instruction.type()) {
case Instruction::Type::SetLocal:
locals[static_cast<Op::SetLocal const&>(instruction).index()] = get(static_cast<Op::SetLocal const&>(instruction).src());
program_counter += sizeof(Op::SetLocal);
goto start;
case Instruction::Type::Mov:
set(static_cast<Op::Mov const&>(instruction).dst(), get(static_cast<Op::Mov const&>(instruction).src()));
program_counter += sizeof(Op::Mov);
goto start;
case Instruction::Type::End:
accumulator = get(static_cast<Op::End const&>(instruction).value());
handle_SetLocal: {
auto& instruction = *reinterpret_cast<Op::SetLocal const*>(&bytecode[program_counter]);
locals[instruction.index()] = get(instruction.src());
DISPATCH_NEXT(SetLocal);
}
handle_Mov: {
auto& instruction = *reinterpret_cast<Op::Mov const*>(&bytecode[program_counter]);
set(instruction.dst(), get(instruction.src()));
DISPATCH_NEXT(Mov);
}
handle_End: {
auto& instruction = *reinterpret_cast<Op::End const*>(&bytecode[program_counter]);
accumulator = get(instruction.value());
return;
case Instruction::Type::Jump:
program_counter = static_cast<Op::Jump const&>(instruction).target().address();
}
handle_Jump: {
auto& instruction = *reinterpret_cast<Op::Jump const*>(&bytecode[program_counter]);
program_counter = instruction.target().address();
goto start;
case Instruction::Type::JumpIf: {
auto& jump = static_cast<Op::JumpIf const&>(instruction);
if (get(jump.condition()).to_boolean())
program_counter = jump.true_target().address();
}
handle_JumpIf: {
auto& instruction = *reinterpret_cast<Op::JumpIf const*>(&bytecode[program_counter]);
if (get(instruction.condition()).to_boolean())
program_counter = instruction.true_target().address();
else
program_counter = jump.false_target().address();
program_counter = instruction.false_target().address();
goto start;
}
case Instruction::Type::JumpTrue: {
auto& jump = static_cast<Op::JumpTrue const&>(instruction);
if (get(jump.condition()).to_boolean()) {
program_counter = jump.target().address();
handle_JumpTrue: {
auto& instruction = *reinterpret_cast<Op::JumpTrue const*>(&bytecode[program_counter]);
if (get(instruction.condition()).to_boolean()) {
program_counter = instruction.target().address();
goto start;
}
program_counter += sizeof(Op::JumpTrue);
DISPATCH_NEXT(JumpTrue);
}
handle_JumpFalse: {
auto& instruction = *reinterpret_cast<Op::JumpFalse const*>(&bytecode[program_counter]);
if (!get(instruction.condition()).to_boolean()) {
program_counter = instruction.target().address();
goto start;
}
case Instruction::Type::JumpFalse: {
auto& jump = static_cast<Op::JumpFalse const&>(instruction);
if (!get(jump.condition()).to_boolean()) {
program_counter = jump.target().address();
goto start;
DISPATCH_NEXT(JumpFalse);
}
program_counter += sizeof(Op::JumpFalse);
goto start;
}
case Instruction::Type::JumpNullish: {
auto& jump = static_cast<Op::JumpNullish const&>(instruction);
if (get(jump.condition()).is_nullish())
program_counter = jump.true_target().address();
handle_JumpNullish: {
auto& instruction = *reinterpret_cast<Op::JumpNullish const*>(&bytecode[program_counter]);
if (get(instruction.condition()).is_nullish())
program_counter = instruction.true_target().address();
else
program_counter = jump.false_target().address();
program_counter = instruction.false_target().address();
goto start;
}
case Instruction::Type::JumpUndefined: {
auto& jump = static_cast<Op::JumpUndefined const&>(instruction);
if (get(jump.condition()).is_undefined())
program_counter = jump.true_target().address();
handle_JumpUndefined: {
auto& instruction = *reinterpret_cast<Op::JumpUndefined const*>(&bytecode[program_counter]);
if (get(instruction.condition()).is_undefined())
program_counter = instruction.true_target().address();
else
program_counter = jump.false_target().address();
program_counter = instruction.false_target().address();
goto start;
}
case Instruction::Type::EnterUnwindContext:
handle_EnterUnwindContext: {
auto& instruction = *reinterpret_cast<Op::EnterUnwindContext const*>(&bytecode[program_counter]);
enter_unwind_context();
program_counter = static_cast<Op::EnterUnwindContext const&>(instruction).entry_point().address();
program_counter = instruction.entry_point().address();
goto start;
case Instruction::Type::ContinuePendingUnwind: {
}
handle_ContinuePendingUnwind: {
auto& instruction = *reinterpret_cast<Op::ContinuePendingUnwind const*>(&bytecode[program_counter]);
if (auto exception = reg(Register::exception()); !exception.is_empty()) {
if (handle_exception(program_counter, exception) == HandleExceptionResponse::ExitFromExecutable)
return;
@ -426,15 +461,17 @@ void Interpreter::run_bytecode(size_t entry_point)
program_counter = m_scheduled_jump.value();
m_scheduled_jump = {};
} else {
program_counter = static_cast<Op::ContinuePendingUnwind const&>(instruction).resume_target().address();
program_counter = instruction.resume_target().address();
// set the scheduled jump to the old value if we continue
// where we left it
m_scheduled_jump = old_scheduled_jump;
}
goto start;
}
case Instruction::Type::ScheduleJump: {
m_scheduled_jump = static_cast<Op::ScheduleJump const&>(instruction).target().address();
handle_ScheduleJump: {
auto& instruction = *reinterpret_cast<Op::ScheduleJump const*>(&bytecode[program_counter]);
m_scheduled_jump = instruction.target().address();
auto finalizer = executable.exception_handlers_for_offset(program_counter).value().finalizer_offset;
VERIFY(finalizer.has_value());
program_counter = finalizer.value();
@ -442,19 +479,18 @@ void Interpreter::run_bytecode(size_t entry_point)
}
#define HANDLE_INSTRUCTION(name) \
case Instruction::Type::name: { \
auto& typed_instruction = static_cast<Op::name const&>(instruction); \
auto result = typed_instruction.execute_impl(*this); \
handle_##name: \
{ \
auto& instruction = *reinterpret_cast<Op::name const*>(&bytecode[program_counter]); \
{ \
auto result = instruction.execute_impl(*this); \
if (result.is_error()) { \
if (handle_exception(program_counter, *result.throw_completion().value()) == HandleExceptionResponse::ExitFromExecutable) \
return; \
goto start; \
} \
if constexpr (Op::name::IsVariableLength) \
program_counter += instruction.length(); \
else \
program_counter += sizeof(Op::name); \
goto start; \
} \
DISPATCH_NEXT(name); \
}
HANDLE_INSTRUCTION(Add);
@ -551,14 +587,8 @@ void Interpreter::run_bytecode(size_t entry_point)
HANDLE_INSTRUCTION(UnaryPlus);
HANDLE_INSTRUCTION(UnsignedRightShift);
case Instruction::Type::Await:
case Instruction::Type::Return:
case Instruction::Type::Yield:
// Handled delicately below.
break;
}
{
handle_Await: {
auto& instruction = *reinterpret_cast<Op::Await const*>(&bytecode[program_counter]);
auto result = instruction.execute(*this);
if (result.is_error()) {
@ -566,9 +596,35 @@ void Interpreter::run_bytecode(size_t entry_point)
return;
goto start;
}
goto may_return;
}
may_return:
handle_Return: {
auto& instruction = *reinterpret_cast<Op::Return const*>(&bytecode[program_counter]);
auto result = instruction.execute(*this);
if (result.is_error()) {
if (handle_exception(program_counter, *result.throw_completion().value()) == HandleExceptionResponse::ExitFromExecutable)
return;
goto start;
}
goto may_return;
}
handle_Yield: {
auto& instruction = *reinterpret_cast<Op::Yield const*>(&bytecode[program_counter]);
auto result = instruction.execute(*this);
if (result.is_error()) {
if (handle_exception(program_counter, *result.throw_completion().value()) == HandleExceptionResponse::ExitFromExecutable)
return;
goto start;
}
goto may_return;
}
may_return: {
auto& instruction = *reinterpret_cast<Instruction const*>(&bytecode[program_counter]);
if (!reg(Register::return_value()).is_empty()) {
will_return = true;
// Note: A `yield` statement will not go through a finally statement,
@ -583,6 +639,7 @@ void Interpreter::run_bytecode(size_t entry_point)
program_counter += instruction.length();
goto start;
}
}
if (!will_yield) {
if (auto handlers = executable.exception_handlers_for_offset(program_counter); handlers.has_value()) {